This invention relates to novel mixtures of substituted aromatic amines which are effective curatives for use in the manufacture of polyurethane-ureas and polyureas, and to the use of such mixtures in the production of polyurethane-urea and polyurea polymers.
3,5-Di(methylthio)-2,6-diaminotoluene (a.k.a. 3,5-di(methylthio)-2,6-toluenediamine) is an effective curative in the preparation of polyurethanes (U.S. Pat. No. 4,982,002). Unfortunately, the compound is very costly to produce, as the intermediate for its production, 2,6-diaminotoluene, is itself very expensive. Thus in practice relatively pure 3,5-di(methylthio)-2,6-diaminotoluene is typically prepared by reacting a commercially-available, relatively low-cost mixture of about 80% 2,4-diaminotoluene and 20% 2,6-diaminotoluene with methyl disulfide to form an approximate 80:20 mixture of 3,5-di(methylthio)-2,4-diaminotoluene and 3,5-di(methylthio)-2,6-diaminotoluene, and subjecting this mixture to rather tedious, time-consuming separation procedures to recover the 2,6-diamino isomer. Also, the reaction rate of 3,5-di(methylthio)-2,6-diaminotoluene with isocyanate prepolymer is relatively fast, and thus handling of the reaction mixture can be difficult.
The approximate 80:20 mixture of 3,5-di(methylthio)-2,4-diaminotoluene and 3,5-di(methylthio)-2,6-diaminotoluene itself is a cost-effective commercially-available curative sold as ETHACURE(copyright) 300 curative by Albemarle Corporation. The product is a low-viscosity, liquid aromatic diamine curative for either2,4- or 80:20 TDI polyether and TDI polyester prepolymers. Cast polyurethane physical properties are comparable to or better than those reported with other typical aromatic diamines.
It would be highly desirable if new polyurethane chain extenders could be found that are easier and thus less costly than pure 3,5-di(methylthio)-2,6-diaminotoluene, that are less reactive with isocyanate prepolymer than 3,5-di(methylthio)-2,6-diaminotoluene, and, if possible, that could produce polyurethane polymers having thermo-mechanical properties at least comparable, if not superior, to those of a mixture formed by methylthiation of a mixture of 80% 2,4-diaminotoluene and 2,6-diaminotoluene as described, for example, in U.S. Pat. No. 4,982,002.
This invention makes it possible to achieve most, if not all, of these desirable objectives.
Pursuant to an embodiment of this invention there is provided a mixture of isomeric alkylthiated mononuclear aromatic amines comprising in the range of about 30 to about 70 mole percent of (i) at least one component of the formula 
and in the range of about 30 to about 70 mole percent of (ii) at least one component of the formula 
wherein Q1 is an alkyl group of from 1 to 4 carbon atoms, Q2 is, independently, a hydrogen atom or an alkyl group of from 1 to 4 carbon atoms, and each R is, independently an alkyl group of from 1 to 4 carbon atoms, and wherein the total percentage of (i) and (ii) in the mixture is at least 90 mole percent, and preferably at least 95 mole percent, such mixture optionally containing up to 10 mole percent, and preferably up to no more than 5 mole percent, of one or more isomers of (i) and (ii).
Pursuant to another embodiment of this invention, Q2 in the above formulas is a hydrogen atom. Thus in this embodiment there is provided a mixture of isomeric alkylthiated mononuclear aromatic amines comprising in the range of about 30 to about 70 mole percent of (i) at least one 3,5-di(alkylthio)-2,6-diamino-1-alkylbenzene and in the range of about 30 to about 70 mole percent of at least one 3,5-di(alkylthio)-2,4-diamino-1-alkylbenzene, such mixture containing at least about 90 mole percent of(i) and (ii), and optionally containing up to 10 mole percent of one or more isomers of (i) and/or (ii). Preferred mixtures contain in the range of about 40 to about 60 mole percent of (i), and in the range of about 40 to about 60 mole percent of (ii), with at least about 95 mole percent of the mixture being (i) and (ii), and optionally up to about 5 mole percent of the mixture being one or more isomers of (i) and/or (ii). Particularly preferred are mixtures as above in which the mixture comprises in the range of about 52 to about 58 mole percent of (i) and in the range of about 42 to about 48 mole percent of(ii), and the total percentage of(i) and (ii) in the mixture is at least 98 mole percent, such mixture optionally containing up to 2 mole percent of one or more isomers of (i) and (ii). In each of these embodiments the two alkylthio groups and the alkyl group in the 1-position each contain, independently, in the range of 1 to 4 carbon atoms. More preferably, the two alkylthio groups are either methylthio or ethylthio groups, most preferably methylthio, and the alkyl group in the 1-position is methyl.
Another embodiment of this invention is the provision of processes of producing polyurethanes using a mixture of isomeric alkylthiated mononuclear aromatic amines of this invention. In one such process a polyurethane-urea cast elastomer is produced by casting into a mold a reaction mixture of an isocyanate prepolymer and a curative comprising at least one mixture of isomeric alkylthiated mononuclear aromatic amines of this invention, and curing the reaction mixture in the mold.
Still another embodiment of this invention is a polyurethane-urea formed by curing an isocyanate prepolymer with a mixture of isomeric alkylthiated mononuclear aromatic amines of this invention. For example, this invention provides a polyurethanexe2x80x94urea polymer produced in accordance with a process of any of originally presented claims 13-24 hereof.
These and other embodiments and features of this invention will be still further apparent from the ensuing description, the accompanying Drawing, and the appended claims.